You're right. It is a low pressure switch. Earlier models did not have it.
The RV2 is a good compressor, much better than what Ford and AMC ran at the time. Not quite as smooth as the GM axial compressor of the day, but a bit more durable. Though all of them worked adequately, they were hp pigs. The Nippondenso/Sanyo compressors that are ubiquitous today need about half the horsepower to maintain the same level of cooling comfort.
